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Mild syntheses and surface characterization of amorphous TiO(OH)(H2PO4)·H2O ion-exchanger
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.ORCID iD: 0000-0002-4533-3920
Tananaev Institute of Chemistry and Technology of Rare Elements and Mineral Raw Materials, Kola Science Center, Russian Academy of Sciences.
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.ORCID iD: 0000-0003-1067-7990
Number of Authors: 42016 (English)In: Materials Chemistry and Physics, ISSN 0254-0584, E-ISSN 1879-3312, Vol. 183, p. 467-475Article in journal (Refereed) Published
Abstract [en]

This work focuses on the synthesis of titanium phosphate (TiP1) ion-exchanger containing solely H2PO4-groups. Based on the elemental analyses, TG, 31P MAS NMR, XRD and Raman data, the formula TiO(OH)(H2PO4)·H2O is assigned to TiP1. The synthesis requires a mild heating at 70–80 °C for a short period of time, followed by filtration and HCl-washing of the TiP1 powder. The layered nature and low crystallinity of this sorbent is confirmed by powder XRD technique. The existence of micro and mesopores in the material is established using BET method. The Na+ capacity of TiP1 is determined to be 6.3 meq g−1 which is the highest value reported for H2PO4-based sorbents. The presence of H2PO4 groups is expected to considerably increase both the pH-working range of the TiP1 sorbent and its exchange capacity towards divalent metal ions. All data for TiP1 are compared to the data for amorphous TiP containing mostly HPO4 groups.

Place, publisher, year, edition, pages
2016. Vol. 183, p. 467-475
National Category
Physical Chemistry
Research subject
Chemistry of Interfaces
Identifiers
URN: urn:nbn:se:ltu:diva-59695DOI: 10.1016/j.matchemphys.2016.09.002ISI: 000386402100057Scopus ID: 2-s2.0-84994031774OAI: oai:DiVA.org:ltu-59695DiVA, id: diva2:1034571
Note

Validerad; 2016; Nivå 2; 2016-10-12 (andbra)

Available from: 2016-10-12 Created: 2016-10-12 Last updated: 2018-08-10Bibliographically approved
In thesis
1. Titanium(IV) Phosphates: The Next Generation of Wastewater Sorbents
Open this publication in new window or tab >>Titanium(IV) Phosphates: The Next Generation of Wastewater Sorbents
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Treatment of industrial waters containing heavy metal ions is essential before being discharged into the environment. Consequently, European regulations have been established to control and limit the amount of heavy metals released. There is a need to develop efficient water treatment techniques that can remove contaminants with respect to these EU regulations.

Ion-exchange is one of the processes that is being investigated due to fast kinetics, high treatment capacity and its ability to remove heavy metal ions present in trace amounts. Titanium phosphates (TiP) are a group of inorganic ion-exchangers that have demonstrated to be particularly selective towards transition metal ions in aqueous solutions. Two types of ion-exchange units are present in TiP material, which are –HPO4 and –H2PO4 groups. Their structural characteristic is highly dependent on the synthesis conditions, which include the source of titanium, temperature, reaction time and P2O5:TiO2 ratio. Most of the studies have been performed on amorphous TiP containing a mixture of both exchange units, with –HPO4 groups being predominant; as crystalline TiP and –H2PO4 based TiP  are often obtained in difficult conditions, high temperature (up to 250 °C) and/or long reaction time (up to 30 days) and/or using autoclave. Despite promising properties depicted in batch conditions, very few data in continuous flow systems (fixed-bed columns) have been reported.

In this work, amorphous TiP composed of entirely –H2PO4 ion-exchange units (TiP1) was synthesized at mild conditions using a TiOSO4 solution and HCl/deionized water as post-synthesis treatments. The sorbent was characterized using a range of techniques (solid-state 31P MAS NMR, Raman, XRD, TGA, BET, Elemental analysis, EXAFS and XANES,) and tested in batch and column set-ups towards single and multi-component waters. The chemical formula of TiP1 was established as TiO(OH)(H2PO4)·H2O and it was found that the synthesis of TiP1 was also dependent on the TiO2/H2SO4 content in the primary titanium solution.

The material displayed a high maximum exchange capacity of ca. 6.4 meq.g-1, expressed as the sodium uptake. The actual ion-exchange capacity towards divalent metal ions was calculated to be ca. 3.4 meq.g-1 in batch condition and up to 4.1 meq.g-1 in fixed-bed column, which is to date the highest recorded for TiP materials. Kinetics of the exchange processes have been studied and the equilibrium was reached within 5-20 minutes. Modeling of the breakthrough curves was achieved using the Thomas model, indicating that the rate driving forces of the processes follow second-order reversible kinetics. The TiP1 sorbent has shown to maintain a high selectivity towards heavy metal ions in multi-component systems (including closed-mine waters) when column studies were performed. The sorption behavior of TiP1 in batch experiments correlates very well with data obtained in fixed-bed column conditions, confirming that prediction of the sorption behavior on the basis of batch data is conceivable.

Another important aspect of this work also involves the mild syntheses of crystalline α-TiP, Ti(HPO4)·H2O, and LTP (Linked Titanium Phosphate) composed of α-TiP and TiP1, where the structural characteristics of these materials were investigated using solid-state NMR, XRD, TGA, EXAFS and XANES.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2018
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Chemical Engineering Chemical Sciences Physical Chemistry
Research subject
Chemistry of Interfaces
Identifiers
urn:nbn:se:ltu:diva-70326 (URN)978-91-7790-178-5 (ISBN)978-91-7790-179-2 (ISBN)
Public defence
2018-09-14, E632, Luleå, 09:00 (English)
Opponent
Supervisors
Available from: 2018-08-13 Created: 2018-08-10 Last updated: 2018-08-28Bibliographically approved

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Trublet, MyleneRusanova-Naydenova, DanielaAntzutkin, Oleg

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